import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
/**
 * 駝峰法-下劃線互轉(zhuǎn)
 * @author cshaper
 * @since 2015.07.04
 * @version 1.0.0
 */
public class UnderlineToCamelUtils {
  
 /**
  * 下劃線轉(zhuǎn)駝峰法
  * @param line 源字符串
  * @param smallCamel 大小駝峰,是否為小駝峰
  * @return 轉(zhuǎn)換后的字符串
  */
 public static String underlineToCamel(String line,boolean smallCamel){
  if(line==null||"".equals(line)){
   return "";
  }
  StringBuffer sb=new StringBuffer();
  Pattern pattern=Pattern.compile("([A-Za-z\\d]+)(_)?");
  Matcher matcher=pattern.matcher(line);
  while(matcher.find()){
   String word=matcher.group();
   sb.append(smallCamel&&matcher.start()==0?Character.toLowerCase(word.charAt(0)):Character.toUpperCase(word.charAt(0)));
   int index=word.lastIndexOf('_');
   if(index>0){
    sb.append(word.substring(1, index).toLowerCase());
   }else{
    sb.append(word.substring(1).toLowerCase());
   }
  }
  return sb.toString();
 }
 /**
  * 駝峰法轉(zhuǎn)下劃線
  * @param line 源字符串
  * @return 轉(zhuǎn)換后的字符串
  */
 public static String camelToUnderline(String line){
  if(line==null||"".equals(line)){
   return "";
  }
  line=String.valueOf(line.charAt(0)).toUpperCase().concat(line.substring(1));
  StringBuffer sb=new StringBuffer();
  Pattern pattern=Pattern.compile("[A-Z]([a-z\\d]+)?");
  Matcher matcher=pattern.matcher(line);
  while(matcher.find()){
   String word=matcher.group();
   sb.append(word.toUpperCase());
   sb.append(matcher.end()==line.length()?"":"_");
  }
  return sb.toString();
 }
}

 public static void main(String[] args) {
  String line="I_HAVE_AN_IPANG3_PIG";
  String camel=underlineToCamel(line,true);
  System.out.println(camel);
  System.out.println(camelToUnderline(camel));
 }

   /***
    * <p>
    * 將駝峰轉(zhuǎn)為下劃線
    * </p >
    * @param str
    * @return java.lang.String
    * @author comapss
    * @date 2022/5/9 0:01
    * @since 1.0.0
   **/
    public static String humpToUnderline(String str) {
        Pattern compile = Pattern.compile("[A-Z]");
        Matcher matcher = compile.matcher(str);
        StringBuffer sb = new StringBuffer();
        while(matcher.find()) {
            matcher.appendReplacement(sb,  "_" + matcher.group(0).toLowerCase());
        }
        matcher.appendTail(sb);
        return sb.toString();
    }

 /***
  * <p>
  * 將下劃線轉(zhuǎn)為駝峰
  * </p >
  * @param str
  * @return java.lang.String
  * @author comapss
  * @date 2022/5/9 0:01
  * @since 1.0.0
 **/
    public static String underlineToHump(String str) {
        str = str.toLowerCase();
        Pattern compile = Pattern.compile("_[a-z]");
        Matcher matcher = compile.matcher(str);
        StringBuffer sb = new StringBuffer();
        while(matcher.find()) {
            matcher.appendReplacement(sb,  matcher.group(0).toUpperCase().replace("_",""));
        }
        matcher.appendTail(sb);
        return sb.toString();
    }